“My mother called me the other day — Laura, I didn’t tell you this — [she] was like: ‘I don’t like that show. I just don’t like it,’ ” Witherspoon, 41, confessed. “She’s like: ‘You’re too mean. It just bothers me how mean you are.’ ”

In the hit HBO miniseries, Dern plays Renata Klein, a high-strung, wealthy businesswoman who feuds with Witherspoon’s scheming type-A character Madeline Mackenzie. The show also stars Nicole Kidman, Shailene Woodley and Zoe Kravitz.

Laura Dern and Reese Witherspoon

Bauer-Griffin/GC Images

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Of course, the two pals aren’t letting their on-screen war affect them off screen. “When I met Reese, I knew she would be my family for the rest of my life,” Dern said. “And I don’t say that lightly.”

“She’s going to piss me off at some point, though,” Witherspoon joked, adding upon Dern’s suggestion they go to therapy that she really meant “a bar.”

“Exactly,” Dern said.

While they hit the bar, their families — including their opinionated mothers — will continue to bond. Last year, the women and their kids even all spent Mother’s Day together.

The bond carries down to the next generation of Dern and Witherspoons.

“Our daughters go out to lunch and dinner and talk, even though they’re just teenagers,” Witherspoon said. “It’s nice for them to have a place to talk about their shared experiences as children of actresses, children in show business.”